Shoemaker-Levy 9 Observations Widespread

Although the Galileo spacecraft was in the best position to
view last July's impacts of Comet Shoemaker-Levy 9 with Jupiter,
two other JPL-managed spacecraft recorded various measurements
from the event.

On its way out of the solar system, Voyager 2, heading south,
observed SL9 with its ultraviolet spectrometer and planetary radio
astronomy instrument.

The Ulysses spacecraft, on its way to explore the sun's polar
regions, made measurements of radio and plasma waves from the
comet's position at about 75 degrees south of the sun's equator
and about 800 million kilometers (500 million miles) from Jupiter.

JPL's Deep Space Network facility at Goldstone, Calif.
performed radio astronomy on the synchrotron emission from
Jupiter's radiation belt, looking for disturbances caused by
Shoemaker-Levy dust.

Also, numerous Lab astronomers and scientists also played a
role in observing the phenomenon. Among them were Drs. Paul Chodas
and Donald Yeomans of the Navigations Systems Section 314, who led
efforts to track ephemeris data, noting the times and locations of
the comet's impacts.

For Galileo's part, some data were available July 18, only two
days after the first impact, via the spacecraft's photopolarimeter
instrument--a small telescope-like meter on Galileo's scan
platform, according to Dr. Terry Martin, science coordinator for
the instrument.

He said the instrument detected infrared light at a wavelength
of 945 nm coming from the H fragment of the comet, its intensity
about 3 percent of the brightness of Jupiter itself.

The impact times predicted by Chodas and Yeomans were off by
only two to 10 minutes.

During the collisions, JPL became the nerve center for Internet
access to SL9 images worldwide. JPL software engineer Ron Baalke
organized a comet "home page" on the World Wide Web system as a
volunteer effort that snowballed into a major clearinghouse of
images attracting worldwide attention and recognition from NASA
Headquarters and the news media.

Besides offering SL9 images delivered by the Hubble Space
Telescope, JPL planetary spacecraft and Lab astronomers using
ground-based equipment, Baalke's Web page garnered submissions
from more than 50 other observatories around the world. The page
eventually offered some 853 images of the impacts of comet
fragments with Jupiter.

The first image, a picture of comet fragment A from the Calar
Alto Observatory, was sent to JPL and appeared on the home page
just three hours after the impact occurred. Fragment Q images were
available on the page just one hour after impact.

During the comet impact week the page handled some 1.1 million
file requests, transferring 24.9 gigabytes, Baalke noted; for all
of 1994 the total was more than 3.2 million files or an estimated
80 gigabytes. The page was accessed by public users in 59
countries.

Because it represented a new phenomenon--the Internet delivering
near-instantaneous science results from an unfolding major story--
the effort also attracted considerable media attention. Baalke's
home page made the front cover of Science magazine in August, for
example, and was featured in an article in Newsweek in September.